The objective of this research is to determine the feasibility of developing a new device for rotator cuff repair that can be used in an arthroscopic procedure. The product is expected to reduce the incidence of re-tears following arthroscopic rotator cuff repair, and to potentially allow a more aggressive rehabilitation, particularly for younger patients. This new device is expected to be used as either an augmentation patch or as an interposition graft, in both acute and chronic rotator cuff repairs. It is estimated that there are now over 250,000 rotator cuff repairs performed each year in the United States, and most of these surgeries are now performed arthroscopically. Yet there is currently no device designed for use in an arthroscopic procedure. The research approach will employ a new absorbable biomaterial, known as TephaFLEX(tm) biomaterial (poly-4-hydroxybutyrate), that has been shown to have high initial strength and prolonged strength retention in vivo, as well as a capacity to remodel in vivo into new tissue. The specific aims of the project are: (1) to produce TephaFLEX(tm) biomaterial in a form suitable for extrusion into multifilament fiber, and to knit the fiber into a mesh scaffold that can be deployed through an arthroscope, resulting in a device with an initial burst strength comparable to current devices used for rotator cuff repair; (2) to test the mesh in vitro to confirm sterility and a lack of cytotoxicity, and (3) implant the mesh scaffold in a small animal model of rotator cuff injury to demonstrate that, after 12 weeks' time, the strength of a repair using this augmentation and/or an interposition scaffold is stronger than that with no such device; and to perform a morphological and histological study on the scaffold explants to assess any inflammatory reaction, appropriate tissue in-growth, and overall suitability of such a scaffold for use in rotator cuff repair. In addition to developing a product that could improve surgical outcomes of rotator cuff repair, this research will also help to introduce a new absorbable medical biomaterial to the medical community that could find additional uses, for example, in other medical devices, in tissue-engineering applications, and for controlled-release drug delivery. [unreadable] [unreadable] [unreadable]